On May 27, 2011, at 10:33 AM, Duncan Murdoch wrote:
> On 27/05/2011 11:11 AM, Martin Maechler wrote:
>> >>>>> Duncan Murdoch<murdoch.dun...@gmail.com>
>> >>>>> on Fri, 27 May 2011 08:23:14 -0400 writes:
>>
>> > On 11-05-27 4:27 AM, Albert-Jan Roskam wrote:
>> >> Aha! Thank you very much for that clarification! It would
>> >> be much more user friendly if R generated a
>> >> NotImplementedError or something similar. The 'garbage
>> >> results' are pretty misleading, esp. to a novice.
>>
>> > I think that's a good idea. The default methods are
>> > documented to work on atomic vectors; dataframes are not
>> > atomic vectors, so it would be reasonable to generate an
>> > error. (See ?is.atomic for a definition of atomic
>> > vectors.)
>>
>> > I'll see if this causes a lot of trouble...
>>
>> > Duncan Murdoch
>>
>> Duncan,
>> do you remember the issue of mean(), var(), median(),... etc
>> that was the topic a few weeks ago ?
>>
>> I strongly advocated that mean.data.frame() should become
>> *deprecated*, and I would propose the same for the functions
>> mentioned here.
>
> I think you may have misunderstood my proposal. Currently is.nan, is.finite
> and is.infinite have no data.frame methods, so the default method is used.
> The problem is that the default method is too permissive: it operates on the
> data.frame by treating it as a list; then it returns FALSE for each list
> element. (If there is only one row, it applies the test to the singleton in
> the column.) This is pretty strange default behaviour.
>
> What I'm proposing is that the default method should trigger an error if you
> try to send it anything that's not atomic. This gives sensible behaviour in
> most cases; the only one where it doesn't work is a list of singletons, which
> used to be handled sensibly, but will now fail.
>
> (There's still a question about what the answer should be for these functions
> when applied to character or raw vectors, which are both atomic. I'm leaning
> towards returning FALSE for every element, which matches the current
> behaviour, but perhaps those should also generate an error.)
>
> I think this partially addresses Bill's objection, but not completely.
> Someone could still put a class on an atomic vector, and that might not be
> handled properly by the default method.
>
>> People should *apply (or *ply) on data frames, and not expect
>> that all kind of functions have data.frame methods
>> which are simply equivalent to basically sapply(<df>,<function>)
>>
>> {and yes -- all this belongs to R-devel rather than R-help}
>
> Where I've moved it now.
>
> Duncan Murdoch
>> Martin
I snipped some of the older content and added Bill.
It seems to me that unless the 'x' argument is both atomic and numeric, these
functions really don't have much utility, if you are going to implement
standard default behavior and more rigorous error checking.
So I would support adding an error message if both conditions are not passed,
rather than an unpredictable result, which an unsuspecting useR might not catch.
I agree that the non-default methods should be deprecated.
Regards,
Marc
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